JP7296279B2 - Shape measuring device and detector calibration method - Google Patents

Description

The present invention relates to a shape measuring device and a method of calibrating a detector mounted on the shape measuring device.

As a method for measuring the straightness of the upper surface of a workpiece to be ground, an on-machine measurement method is known in which a displacement gauge is attached to the grinding wheel head to scan the surface to be processed, using the workpiece feeding function of the grinding apparatus. In the on-machine measurement method, a sequential three-point method using a detector including three displacement gauges is generally used (for example, Patent Document 1). In the sequential three-point method, the positions in the height direction of three points positioned on a straight line on the upper surface of the workpiece are measured simultaneously, and the degree of local bending (curvature) of the plane is obtained from the measurement results. The curvature is integrated twice to obtain the straightness of the upper surface of the work by calculation. Straightness means the degree of deviation of a target shape from a geometrically correct straight line. Measuring the straightness of the upper surface of the work is equivalent to measuring the shape of unevenness in the height direction of the upper surface of the work.

In order to accurately measure the straightness of the surface of the object to be measured, it is necessary to calibrate the zero point of the detector so that the zero points of the three displacement gauges are positioned on the geometrically correct plane. A reference device with a highly straight reference surface is used to calibrate the zero point of the detector. When measuring the straightness of the upper surface of a work ground by a grinding machine, for example, a standard is placed on the work after grinding so that the zero points of the three displacement gauges are positioned on the reference plane. Then perform zero point calibration of the detector.

JP 2016-166873 A

After zero-point calibration of the detector, if the straightness of the reference surface is measured by setting the reference device at another position on the workpiece, the straightness geometric tolerance is ideally zero. However, it was found that if the straightness of the reference surface is measured by changing the position of the reference device, the geometric tolerance of the straightness of the reference surface may not be zero. This means that the position of the zero point after zero point calibration varies depending on the position where the reference device is placed. Without high-precision zero-point calibration, the straightness measurement accuracy of the upper surface of the workpiece is lowered.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a shape measuring apparatus and a method for calibrating a detector in which variation in the position of the zero point is less likely to occur in the zero point calibration of the detector .

According to one aspect of the invention,
a detector that includes at least three displacement gauges arranged in a line and is arranged facing the measurement object to detect the displacement of the distance from the at least three displacement gauges to the measurement object;
a datum supported on a support member to provide a reference surface for calibration of the detector;
and a controller for calibrating the detector ,
The reference device has a support structure supported on the support member at two points in the direction in which the at least three displacement gauges are arranged,
The control device is provided with a shape measuring device that calibrates the detector with the reference plane facing the at least three displacement gauges.

According to another aspect of the invention,
a detector that includes at least three displacement gauges arranged in a row and is arranged facing the object to be measured to detect the displacement of the distance from each of the at least three displacement gauges to the object to be measured; ,
a datum supported on a support member to provide a reference surface for calibrating the detector;
and a controller for calibrating the detector ,
In a state in which the reference device is supported on the support member, it is bent by its own weight, and the shape of the reference surface in the bent state is not affected by the unevenness of the upper surface of the support member. ,
The control device is provided with a shape measuring device that calibrates the detector with the at least three displacement gauges facing the reference plane.

According to yet another aspect of the invention,
Calibration of a detector that detects the displacement of the distance from each of the at least three displacement gauges to the measurement object by arranging at least three displacement gauges arranged in a line so as to face the measurement object a method,
supporting the reference device on a supporting member at two points in the direction in which the at least three displacement gauges are arranged, in a posture in which the reference surface of the reference device faces the at least three displacement gauges;
A calibration method is provided for calibrating the detector with the at least three displacement gauges facing the reference plane.

The bending shape of the standard is not affected by the unevenness of the upper surface of the support member. Therefore, when calibrating the detector, a reference plane with small variations in shape is provided, and as a result, it is possible to suppress variations in the positions of the zero points of at least three displacement gauges of the detector depending on the installation location.

FIG. 1A is a perspective view of a grinding apparatus incorporating a shape measuring device according to an embodiment, and FIG. 1B is a side view of the detector with the detector attached to the grindstone head. FIG. 2 is a schematic diagram showing the upper surface of the workpiece to be measured and the detector. FIG. 3 is a schematic diagram showing the positional relationship between the first displacement gauge, the second displacement gauge, the third displacement gauge of the detector and the reference device. 4A and 4B are cross-sectional views showing a state in which a reference device used in a detector calibration method according to a comparative example is placed on a workpiece. FIG. 5 is a perspective view of the standard device used in the shape measuring apparatus according to the embodiment, viewed obliquely from below. 6A and 6B are cross-sectional views showing a state in which the reference device used in the shape measuring apparatus according to the embodiment is placed on the upper surface of the work. FIG. 7A is a schematic diagram of a reference device having a beam structure with an evenly distributed load supported at both ends, and FIG. 7B is a schematic diagram showing the positional relationship between the reference device and the detector used in the shape measuring apparatus according to the embodiment. . 8A to 8C are diagrams showing the positional relationship of the workpiece, reference device, and detector during the evaluation experiment. FIG. 9A is a graph showing the distribution of the offset amount g measured using a rectangular parallelepiped standard without legs, and FIG. 9B is a standard used in the shape measuring device according to the embodiment (FIG. 5) , that is, a graph showing the distribution of the offset amount g measured using a reference device having legs. FIG. 10 is a flow chart of a shape measuring method according to an embodiment. 11A is a diagram showing an image of the control window displayed on the display of the input/output device by the control device, and FIG. 11B is a diagram showing an example of the image of the measurement results displayed on the display of the input/output device. . FIG. 12 is a flow chart of a shape measuring method according to another embodiment. 13 is a diagram showing an image of a control window displayed on the display of the input/output device (FIG. 1A) by the control device of the embodiment shown in FIG. 12. FIG. FIG. 14 is a graph showing the measurement result of the straightness geometrical tolerance of the upper surface of the work and the time change of the temperature measured by the temperature sensor (FIG. 1B). FIG. 15A is a diagram showing an image of a control window displayed on the display of the input/output device (FIG. 1A) by the control device of the shape measuring device according to still another embodiment, and FIG. ) is a diagram showing an example of an image displayed on the display. 16A to 16D are perspective views of a reference device according to a modification of the embodiment shown in FIG. 5, as viewed obliquely from below. 17A is a side view of a reference device in a weightless state according to another modification of the embodiment shown in FIG. 5, and FIG. 17B is a side view of the reference device installed on the upper surface of a work.

A shape measuring apparatus according to an embodiment will be described with reference to FIGS. 1A to 11B.
FIG. 1A is a perspective view of a grinding machine incorporating a shape measuring device according to this embodiment. The grinding apparatus includes a movable table 10 , a table guide mechanism 11 , a grindstone head 15 , a grindstone 16 , a guide rail 18 , a control device 20 , an input/output device 21 , a reference device 30 and a detector 40 . A table guide mechanism 11 reciprocates the movable table 10 in one direction in a horizontal plane. A workpiece 12 to be ground is supported on a movable table 10 . This workpiece 12 corresponds to a measurement object whose straightness is measured by the shape measuring device.

A grinding wheel head 15 is supported above the workpiece 12 on the movable table 10 by a guide rail 18 so as to be able to move up and down. The grindstone head 15 can move in a direction perpendicular to the moving direction of the movable table 10 within a horizontal plane. An xyz orthogonal coordinate system is defined in which the moving direction of the movable table 10 is the x-axis direction, the moving direction of the grindstone head 15 is the y-axis direction, and the vertical downward direction is the positive direction of the z-axis.

A grindstone 16 is attached to the lower end of the grindstone head 15 . The grindstone 16 has a columnar shape and its central axis is parallel to the y-axis direction. The work 12 is ground by lowering the grindstone head 15 until the grindstone 16 contacts the work 12 and moving the work 12 in the x-axis direction while rotating the grindstone 16 . By moving the grindstone head 15 in the y-axis direction and repeating the same processing, the entire upper surface of the workpiece 12 can be ground.

The control device 20 controls movement of the movable table 10 in the x-axis direction, movement and elevation of the grindstone head 15 in the y-axis direction, and rotation of the grindstone 16 . Various commands are input from the input/output device 21 to the control device 20 , and processing results and the like by the control device 20 are output to the input/output device 21 . The input/output device 21 includes, for example, a display, pointing device, keyboard, and the like.

The detector 40 is detachably attached to the side surface of the grindstone head 15 . During grinding, the detector 40 is removed from the grindstone head 15 . A detector 40 is attached to the grindstone head 15 when measuring the straightness of the upper surface of the work 12 . The detector 40 is attached to the grindstone head 15 by, for example, magnetic attraction, screwing, or the like. The configuration of detector 40 will be described in detail later with reference to FIG. 1B. When calibrating the detector 40 , the reference device 30 is placed above the workpiece 12 . The datum 30 provides a reference plane for calibration of the detector 40 by being supported on the workpiece 12 . The workpiece 12 functions as a support member for supporting the reference device 30 during zero point calibration.

FIG. 1B is a side view of the detector 40 with the detector 40 attached to the grindstone head 15. FIG.

The detector 40 includes a first displacement gauge 42a, a second displacement gauge 42b, and a third displacement gauge 42c that are attached to the support base 41 and arranged in a row in the x-axis direction. As these displacement gauges, for example, non-contact laser displacement gauges can be used. Each of the first displacement gauge 42 a , the second displacement gauge 42 b , and the third displacement gauge 42 c is arranged to face the work 12 to detect the displacement of the distance from each displacement gauge to the work 12 . More specifically, the distance in the z-axis direction from the zero point of each displacement gauge to the point to be measured on the upper surface of the workpiece 12 is measured. In a state where the reference device 30 (FIG. 1A) is arranged at a position facing the detector 40, each displacement meter detects the displacement of the reference surface of the reference device 30 in the z-axis direction.

A temperature sensor 45 is further attached to the support base 41 . A temperature sensor 45 measures the temperature of the detector 40 . The measured values of the first displacement gauge 42a, the second displacement gauge 42b, and the third displacement gauge 42c, and the measured value of the temperature sensor 45 are input to the controller 20 (FIG. 1A).

Next, a method for measuring the straightness of the upper surface of the workpiece 12 will be described with reference to FIG.
FIG. 2 is a schematic diagram showing the upper surface of the workpiece 12 to be measured and the detector 40. As shown in FIG. The upper surface of the workpiece 12 is arranged substantially parallel to the xy plane. In addition, in FIG. 2, the minute irregularities on the upper surface of the workpiece 12 are shown in an exaggerated manner. A first displacement gauge 42a, a second displacement gauge 42b, and a third displacement gauge 42c of the detector 40 are arranged in a row at a pitch P in the x-axis direction.

When zero point calibration is performed for three displacement gauges, ideally the zero points A ₀ , B ₀ , and C ₀ of the first displacement gauge 42a, the second displacement gauge 42b, and the third displacement gauge 42c are: They are arranged at a pitch P on a straight line substantially parallel to the x-axis. In this embodiment, as will be described later with reference to FIGS. 7A and 7B, the three zero points A ₀ , B ₀ , and C ₀ are not strictly arranged on a straight line. Assume that three zero points A ₀ , B ₀ , C ₀ are aligned.

The first displacement gauge 42 a measures the distance _Da from the zero point A ₀ to the point A to be measured on the upper surface of the workpiece 12 . Similarly, the second displacement gauge 42b and the third displacement gauge 42c measure the distance Db from the zero point _B0 to the measured point _B and the distance _Dc from the zero point _C0 to the measured point C, respectively. .

The distance between the line segment connecting the points A and C to be measured and the point B to be measured in the z-axis direction is called an offset amount g. The offset amount g is represented by the following formula.

The curvature d ² z/dx ² (x=B) of the upper surface of the workpiece 12 at the point B to be measured by the second displacement gauge 42b can be expressed by the following equation.

While moving one of the detector 40 and the workpiece 12 with respect to the other in the x-axis direction, the offset amount g is measured by Equation (1). The straightness of the upper surface (that is, the shape of the surface in the xz cross section) can be obtained by performing the second-order integration of the curvature distribution of the upper surface of the work 12 obtained using the equations (1) and (2).

Next, the principle of zero point calibration of the detector 40 will be described with reference to FIG.
FIG. 3 is a schematic diagram showing the positional relationship between the first displacement gauge 42a, the second displacement gauge 42b, and the third displacement gauge 42c of the detector 40 and the reference device 30. As shown in FIG.

A reference device 30 is placed on the upper surface of the work 12 and the reference surface 31 is made to face the detector 40 . In this state, the points to be measured on the reference plane 31 of the first displacement gauge 42a, the second displacement gauge 42b, and the third displacement gauge 42c are respectively set to the first displacement gauge 42a, the second displacement gauge 42b, and the third displacement gauge 42b. They are set as zero points A ₀ , B ₀ , and C ₀ of the 3-displacement meter 42c.

Note that the zero points A ₀ , B ₀ , and C ₀ may be set based on the average value of the measured values obtained by performing a plurality of measurements while moving the reference device 30 in the x-axis direction with respect to the detector 40. . A process of performing a plurality of measurements while moving the reference device 30 in the x-axis direction is referred to as scanning. Movement of the reference device 30 is achieved by moving the workpiece 12 in the x-axis direction by the table guide mechanism 11 . By adopting this method, it is possible to reduce variations in the zero point due to the surface roughness of the reference surface 31 . Furthermore, the position of the point to be measured on the reference plane 31 is changed in the y-axis direction and scanning is performed multiple times, and the zero points A ₀ , B ₀ , _C0 may be set. Note that even if the mounting positions of the first displacement gauge 42a, the second displacement gauge 42b, and the third displacement gauge 42c to the support base 41 vary in the z-axis direction, the reference plane 31 is a geometrically correct plane. If so, the zero points A ₀ , B ₀ , and C ₀ will be positioned on a straight line by zero point calibration.

Next, a method of calibrating the detector 40 using the reference device 30 according to the comparative example will be described with reference to FIGS. 4A and 4B.

4A and 4B are cross-sectional views of a state in which the reference device 30 according to the comparative example is placed on the workpiece 12. FIG. When calibrating the detector 40, a rectangular parallelepiped standard 30 is placed on the upper surface of the workpiece 12 so that its length direction is parallel to the x-axis. Although the upper surface of the workpiece 12 after grinding is substantially flat, in reality, minute irregularities remain. Therefore, the reference device 30 is supported by the workpiece 12 at approximately two points in its length direction. The reference device 30 is made of, for example, a hard-to-deform ceramic material having a Young's modulus of about 130 GPa, but slightly bends due to its own weight with the point in contact with the workpiece 12 as a fulcrum.

In the example shown in FIG. 4A, the reference device 30 is supported in contact with the workpiece 12 near both longitudinal ends. In this case, the reference device 30 is flexed into a downward convex shape. In the example shown in FIG. 4B, the reference device 30 is supported in contact with the workpiece 12 near the center in the length direction. In this case, the reference device 30 is flexed into an upward convex shape. If the zero point calibration of the detector 40 is performed with the reference plane 31 bent, the three zero points A ₀ , B ₀ , and C ₀ will not be positioned on a straight line. In addition, the relative positional relationship between the three zero points A ₀ , B ₀ , and C ₀ varies depending on the position where the reference device 30 is installed.

Deflection occurring in the reference device 30 is affected by the uneven shape of its supporting surface (that is, the upper surface of the workpiece 12). Therefore, it is not possible to accurately estimate the shape of the reference surface 31 in the state in which the bending occurs. Therefore, it is difficult to correct the three zero points A ₀ , B ₀ , and C ₀ to arrange them on a straight line.

Next, a method of zero-point calibration of the detector 40 using the reference device 30 used in the shape measuring apparatus according to this embodiment will be described with reference to FIGS. 5 to 7B.

FIG. 5 is a perspective view of the reference device 30 used in the shape measuring apparatus according to the embodiment, viewed obliquely from below. The reference device 30 includes a main member 32 having a rectangular parallelepiped shape elongated in one direction. The upper surface of the main member 32 is used as the reference surface 31 . Three legs 33 are attached to the bottom surface of the main member 32 opposite to the reference surface 31 . One leg 33 is attached to one longitudinal end of the bottom surface of the datum 30 and the other two legs 33 are attached to the other end. Also, the two legs 33 are attached at intervals in the width direction orthogonal to the length direction. That is, the two legs 33 are attached at the same position in the length direction and at different positions in the width direction.

Each of the legs 33 has a hemispherical shape and is adhered to the bottom surface of the main member 32 on its flat surface. An adhesive, a double-sided tape, or the like can be used for bonding the leg portion 33 . A hard material such as zirconia is used for the leg portion 33 . The height of the legs 33 is, for example, 2 mm or more and 15 mm or less, typically 7 mm. However, the height of the leg portion 33 is not limited to this range. The height of the leg portion 33 may be such that the bottom surface of the main member 32 of the reference device 30 does not contact the upper surface of the work 12 when the reference device 30 is placed on the upper surface of the work 12 .

6A and 6B are cross-sectional views showing a state in which the reference device 30 used in the shape measuring apparatus according to the embodiment is placed on the upper surface of the workpiece 12. FIG. The uneven shape of the upper surface of the work 12 shown in FIGS. 6A and 6B is the same as the uneven shape of the upper surface of the work 12 shown in FIGS. 4A and 4B. 6A and 6B, the reference device 30 is supported on the workpiece 12 by contacting the upper surface of the workpiece 12 with the three legs 33 . The reference device 30 does not contact the workpiece 12 at locations other than the three legs 33 .

Since two of the three legs 33 are arranged at the same position in the length direction, the reference device 30 is supported on the workpiece 12 at two locations in the length direction. Therefore, the reference device 30 has a beam structure with uniform load distribution supported at both ends. Since the reference device 30 is always supported on the support surface at two points in the longitudinal direction regardless of the shape of the unevenness of the support surface, the shape and magnitude of the bending of the reference device 30 depend on the shape of the unevenness of the support surface. Not affected.

FIG. 7A is a schematic diagram of a reference device 30 having a beam structure with a uniform load distribution supported at both ends. Let L be the length of the reference device 30, w be the load per unit length, E be the Young's modulus, and I be the second elastic moment. ) is represented by the following formula.

The shape and magnitude of the deflection occurring in the reference surface 31 when the reference device 30 is placed on the upper surface of the work 12 can be obtained in advance using equation (3). Information defining the shape of this deflection is stored in controller 20 (FIG. 1A).

FIG. 7B is a schematic diagram showing the positional relationship between the reference device 30 and the detector 40 used in the shape measuring device according to the embodiment. The reference plane 31 is flexed as shown in FIG. 7A. In FIG. 7B, the amount of deflection is exaggerated from the actual amount of deflection. The height of the reference plane 31 is detected by the first displacement gauge 42a, the second displacement gauge 42b, and the third displacement gauge 42c of the detector 40, and zero point calibration is performed. Thereby, zero point A ₀ , zero point B ₀ , and zero point C ₀ are set on the reference plane 31 .

The intersection of a straight line passing through the zero point _B0 and parallel to the z-axis and a line segment connecting the zero points _A0 and _C0 is defined as the true zero point _B01 of the second displacement meter 42b. Let the distance between the zero point _B0 and the true zero point _B01 be the zero point offset amount _g0 . The deflection shape of the reference plane 31 can be obtained by calculation from equation (3), and since the information defining the shape is stored in advance in the control device 20 (FIG. 1A), the zero point offset amount g ₀ can be calculated by can ask. The controller 20 stores the calculated zero point offset amount _g0 . In order to strictly calculate the straightness of the upper surface of the workpiece 12 at the true zero point _B01 , it is preferable to use the true zero point _B01 as the zero point of the second displacement gauge 42b. That is, it is preferable to correct the offset amount g (FIG. 2) to correspond to the zero point offset amount _g0 . Specifically, it is preferable to calculate the offset amount g by the following formula instead of formula (1).

Next, with reference to FIGS. 8A to 9B, an evaluation experiment conducted to confirm that the bending shape of the reference device 30 is not affected by the unevenness of the upper surface of the workpiece 12 and the results thereof will be described.

8A to 8C are diagrams showing the positional relationship among the workpiece 12, the reference device 30, and the detector 40 when performing the evaluation experiment. First, as shown in FIG. 8A, the reference device 30 is placed on the region R1 of the workpiece 12, and the offset amount g (FIG. 2) is calculated by the detector 40, which has been zero-point calibrated, using the equation (1). to measure The reference device 30 is moved within the region R1 and the offset amount g is measured multiple times using the equation (1).

Next, as shown in FIG. 8B, the reference device 30 is moved above the region R2 of the workpiece 12, and the offset amount g is similarly measured a plurality of times. Further, as shown in FIG. 8C, the reference device 30 is moved above the region R3 of the workpiece 12, and the offset amount g is similarly measured a plurality of times.

FIG. 9A is a graph showing the distribution of the offset amount g measured using the rectangular parallelepiped reference device 30 having no legs 33. FIG. FIG. 9B is a graph showing the distribution of the offset amount g measured using the reference device 30 (FIG. 5) used in the shape measuring device according to the embodiment, that is, the reference device 30 having the legs 33. FIG. The horizontal axes of the graphs of FIGS. 9A and 9B correspond to the regions R1, R2, and R3, and the vertical axes represent the offset amount g. One black circle symbol in the graph indicates the offset amount g calculated by one measurement. A plurality of black circle symbols are displayed in one region because in each of the regions R1, R2, and R3, measurements were performed a plurality of times by moving the reference device 30 within the region.

When the reference device 30 without the legs 33 is used, as shown in FIG. , there is a difference in magnitude of the offset amount g. Overall, the offset amount g varies by about 0.075 μm. This means that the shape of the reference plane 31 after the bending of the reference device 30 differs according to the place where the reference device 30 is installed.

On the other hand, when the reference device 30 having the legs 33 is used, as shown in FIG. no. Variations in the offset amount g are within the range of 0.02 μm or less. This means that the shape of the reference surface 31 after bending of the reference device 30 is substantially constant regardless of the place where the reference device 30 is installed. Also, the calculated value of the offset amount g is approximately equal to the zero point offset amount g ₀ (FIG. 7B).

According to the evaluation experiments shown in FIGS. 8A to 9B, by using the reference device 30 having the legs 33, the bending shape of the reference device 30 hardly depends on the uneven shape of the support surface supporting the reference device 30. was confirmed.

Next, a method for measuring the straightness of the upper surface of the workpiece 12 (FIG. 1A) with the shape measuring apparatus according to the embodiment will be described with reference to FIGS. 10 to 11B.

FIG. 10 is a flow chart of a shape measuring method according to an embodiment.
After the work 12 has been ground, the operator attaches the detector 40 to the grindstone head 15 (step SA01) and installs the reference device 30 on the work 12 (step SA02). After that, the zero point calibration of the detector 40 is performed using the reference plane 31 of the reference device 30 . After the zero point calibration of the detector 40 is completed, the reference device 30 is removed from the workpiece 12 .

The grindstone head 15 (FIG. 1A) is moved in the y-axis direction to the measurement location of the workpiece 12 (step SA05). After that, the straightness of the upper surface of the workpiece 12 along one line parallel to the x-axis direction is measured (step SA06). Specifically, the controller 20 (FIG. 1A) controls the first displacement gauge 42a, the second displacement gauge 42b and the third displacement gauge 42c of the detector 40 while moving the workpiece 12 in the x-axis direction. Take measurements at time intervals. Based on the obtained measured values, the shape of the upper surface of the workpiece 12 is determined by the sequential three-point method described with reference to FIG. At this time, the offset amount g is calculated using equation (4).

After measuring the straightness of the upper surface of the workpiece 12 along one line, the measurement result is output to the input/output device 21 (FIG. 1A) (step SA07). When measuring the straightness along another line, the steps from the step of setting the reference device 30 on the workpiece 12 (step SA02) to the step of outputting the measurement result (step SA07) are repeated (step SA08). After measuring the straightness along all the lines to be measured on the upper surface of the workpiece 12, the measurement is completed.

11A is a diagram showing an image of a control window displayed on the display of the input/output device 21 by the control device 20. FIG. The control window includes a measurement display pane 22 , a preferences pane 23 and a calibration pane 24 . Furthermore, a measurement start button 26 is displayed in the control window.

The measurement display pane 22 includes output fields that display the measurements of the first displacement gauge 42a, the second displacement gauge 42b, and the third displacement gauge 42c. The basic setting pane 23 displays data input fields for inputting the length of the workpiece 12 (dimension in the x-axis direction), the moving speed of the movable table 10 during measurement, and the number of reciprocating measurements. The number of round trips for measurement is input, for example, in the form of a pull-down menu. The calibration pane 24 displays an output field displaying the zero point value and a calibration start button 25 .

When the operator selects calibration start button 25, controller 20 (FIG. 1A) performs zero point calibration of detector 40 (step SA03). Selection of a button is performed, for example, by moving the cursor of the mouse to the button and clicking the mouse, tapping the button, or the like. The zero point output field displays the value of the offset amount g calculated using equation (1). At the time of zero point calibration, the distances D _a , D _b , and D _c (FIG. 2) are all reset to zero, so the number displayed in the zero point output field is zero.

When the operator selects the measurement start button 26, the controller 20 measures the straightness of the top surface of the workpiece 12 along one line (step SA06).

FIG. 11B is a diagram showing an example of an image of measurement results displayed on the display of the input/output device 21. As shown in FIG. The position of the upper surface of the work 12 in the height direction is displayed in a graph format on the display. The horizontal axis represents the position in the length direction (x-axis direction) of the workpiece 12, and the vertical axis represents the amount of surface displacement (position in the z-axis direction). The linear component of the height variation is removed, and the surface displacement amount is corrected so that the heights at both ends of the workpiece 12 are both zero. FIG. 11B shows an example with a profile that is lower in the middle than at the ends. The absolute value of the position (the lowest point of the curve in FIG. 11B) where the amount of displacement from 0 on the upper surface of the workpiece 12 is the largest corresponds to the straightness geometrical tolerance. In the example shown in FIG. 11B, the straightness geometric tolerance is about 22 μm.

Next, the excellent effects of the above embodiment will be described.
In the above-described embodiment, the bending shape of the reference device 30 is constant regardless of the position on the workpiece 12 where the reference device 30 is installed during zero point calibration. Therefore, the relative positional relationship among the three zero points A ₀ , B ₀ , C ₀ can be kept constant. Furthermore, in the above embodiment, the zero point A ₀ of the first displacement gauge 42a, the true zero point B ₀₁ of the second displacement gauge 42b, and the zero point C ₀ of the third displacement gauge 42c are positioned on a straight line. By measuring the straightness of the upper surface of the workpiece 12 with reference to the three zero points A ₀ , B ₀₁ , and C ₀ located on a straight line, the straightness measurement accuracy can be improved.

Next, a shape measuring device and a shape measuring method according to another embodiment will be described with reference to FIGS. 12 to 14. FIG. The description of the configuration common to the embodiment shown in FIGS. 1A to 11B will be omitted below.

FIG. 12 is a flow chart of the shape measuring method according to this embodiment.
In the embodiment shown in FIG. 10, every time the straightness of the upper surface of the workpiece 12 is measured along one line (step SA06), zero point calibration of the detector 40 is performed (step SA03) before the measurement. . On the other hand, in the embodiment shown in FIG. 12, the difference between the temperature measured at the present time by the temperature sensor 45 (FIG. 1B) and the temperature measured immediately before the zero point calibration is less than or equal to the threshold. If there is, the process of zero point calibration (steps SA02 to SA04) is omitted (step SA10). Only when the difference between the current temperature measurement value by the temperature sensor 45 (FIG. 1B) and the temperature measurement value when the zero-point calibration was performed immediately before exceeds the threshold value, the zero-point calibration processing (step SA02 ~ SA04) is executed again.

FIG. 13 shows an image of a control window displayed by the control device 20 on the display of the input/output device 21 (FIG. 1A). In this embodiment, in the calibration pane 24, in addition to the zero point output field and the calibration start button 25, there are displayed output fields that respectively display the temperature at the time of calibration, the time of calibration, and the current temperature. Furthermore, a temperature measurement button 27 is displayed.

In the calibration temperature output field, the controller 20 displays the temperature measured by the temperature sensor 45 during the most recent zero point calibration. In the calibration time output field, the controller 20 displays the time of the most recent zero point calibration. In the current temperature output field, the controller 20 displays the current temperature measured by the temperature sensor 45 . When the operator selects the measure temperature button 27, the controller 20 obtains the current temperature reading from the temperature sensor 45 and updates the reading displayed in the current temperature output field.

If the difference between the temperature at the time of the most recent zero point calibration and the current temperature exceeds a threshold, the controller 20 displays a message 28 in the calibration pane 24 prompting the zero point calibration to be performed again. . Note that, instead of the message 28, other alerting information such as a voice prompting execution of zero point calibration, an alarm sound, or the like may be output.

FIG. 14 is a graph showing the measurement result of the straightness geometrical tolerance of the upper surface of the workpiece 12 and the time change of the temperature measured by the temperature sensor 45 (FIG. 1B). A process of measuring the straightness along each of the six lines L1 to L6 parallel to the x-axis on the upper surface of the workpiece 12 was performed 10 times, and the straightness geometrical tolerance was obtained for each measurement process. Each of the plurality of black circle symbols shown in FIG. 14 indicates the calculation result of the straightness geometrical tolerance obtained in one measurement process.

Zero point calibration of the detector 40 was performed before the straightness measurement along the line L1. After that, the zero point calibration of the detector 40 was not performed from the straightness measurement along the line L1 to the straightness measurement along the line L5. After measuring the straightness along the line L5, the detector 40 was zero-point calibrated before measuring the straightness along the line L6.

During the period from the start of the straightness measurement along the line L1 to the end of the straightness measurement along the line L4, the temperature measured by the temperature sensor 45 hardly changed. Measured straightness geometrical tolerance along each line from line L1 to line L4 measured during a period in which the temperature was substantially constant was substantially constant.

After measuring straightness along line L4, the temperature began to rise due to external factors. When the straightness along the line L5 was measured while the temperature was increased, the measured straightness geometrical tolerance was significantly different from the straightness geometrical tolerance measured before the temperature was increased.

When the zero-point calibration was performed again and the straightness geometrical tolerance along line L6 was measured, the measured straightness geometrical tolerance along each of lines L1 to L4 measured before the temperature rise was almost equal to the measured value. Got. Although the temperature slightly decreased due to an external factor after the straightness measurement along the line L5, the temperature remained higher than the temperature when the straightness along each of the lines L1 to L4 was measured. .

The following two findings are obtained from the measurement results shown in FIG.
First, if the temperature around the detector 40 does not fluctuate, straightness can be measured with high accuracy without performing zero point calibration. Secondly, if the temperature around the detector 40 changes to some extent, the accuracy of straightness measurement will decrease. can be done.

Next, the excellent effects of the embodiment shown in FIGS. 12 to 14 will be described.
In this embodiment, as shown in FIG. 13, the display of the input/output device 21 (FIG. 1A) displays the temperature at the most recent zero point calibration and the current temperature. The operator can easily determine whether or not to perform zero point calibration again by looking at this temperature display. Specifically, when the temperature change exceeds the threshold, the zero point calibration should be performed again. This threshold is preferably determined in advance according to the accuracy required for straightness measurement. For example, 0.5° C. may be set as the threshold. In addition, by displaying the message 28 prompting the user to perform the zero point calibration, it is possible to prevent the operator from forgetting to perform the zero point calibration.

Also, in this embodiment, the time when the most recent zero point calibration was performed is displayed. If the detector 40 has the characteristic that the measured value drifts over time for some reason, should the operator re-execute the zero-point calibration based on the elapsed time since the most recent zero-point calibration? You can decide whether or not

Furthermore, in this embodiment, as shown in FIG. 12, when the temperature change is equal to or less than the threshold value, straightness measurement along the next line on the upper surface of the workpiece 12 is performed without performing zero point calibration. The total time required for measuring the straightness of the upper surface of the workpiece 12 can be shortened.

Next, a shape measuring apparatus according to still another embodiment will be described with reference to FIGS. 15A and 15B. The description of the configuration common to the embodiment shown in FIGS. 1A to 11B will be omitted below.

FIG. 15A is a diagram showing an image of a control window displayed by control device 20 on the display of input/output device 21 (FIG. 1A). In this embodiment, a past measurement result pane 29 is displayed in the control window. In the past measurement result pane 29, a "Select past measurement result" button is displayed.

When the operator selects the "Select Past Measurement Results" button, the control device 20 (FIG. 1A) displays on the display a list of storage locations of straightness measurement data that has been measured and accumulated in the past. The operator can select at least one straightness measurement data from this list.

FIG. 15B is a diagram showing an example of an image displayed on the display of the input/output device 21 (FIG. 1A). In the embodiment shown in FIG. 11B, the surface profile corresponding to the currently measured straightness is displayed in graphical form on the display. On the other hand, in this embodiment, the straightness measured at the present time and the straightness measured in the past selected by the operator are superimposed and displayed on one graph as the distribution of the amount of surface displacement. In FIG. 15B, a thick solid line and a thin solid line indicate the straightness measured at present and the straightness measured in the past, respectively.

Next, the excellent effects of this embodiment will be described.
In this embodiment, the operator can easily compare the currently measured straightness of the upper surface of the workpiece 12 with the previously measured straightness of the upper surface of the workpiece 12 . For example, when one work 12 is ground for the first time, and then the cutting depth of the grindstone 16 is increased to perform the second grinding, the straightness after the first grinding and The straightness after the second grinding process can be easily compared. This comparison result is useful as basic information for estimating the necessity of additional grinding and processing conditions for additional grinding, such as the additional depth of cut of the grindstone 16 .

Reference device 30 according to a modification of the embodiment shown in FIG. 5 will now be described with reference to FIGS. 16A to 16D.

16A to 16D are perspective views of the datum 30 according to a modification of the embodiment shown in FIG. 5, as viewed obliquely from below. In the embodiment shown in FIG. 5, three hemispherical legs 33 are attached to the bottom surface of the main member 32 at both longitudinal ends. On the other hand, in the modification shown in FIG. 16A, three legs 33 are attached to the bottom surface of the main member 32 slightly inward from both ends in the length direction. Two legs 33 out of the three legs 33 are attached at the same lengthwise position as in the embodiment shown in FIG. Therefore, the reference device 30 is supported on the upper surface of the workpiece 12 at two locations in the length direction.

In the modification shown in FIG. 16B, the leg portion 33 has a rectangular parallelepiped shape elongated in the width direction of the main member 32 . Two legs 33 are attached to both longitudinal ends of the bottom surface of the main member 32, respectively. In the modification shown in FIG. 16B as well, the reference device 30 is supported on the upper surface of the workpiece 12 at two points in the length direction.

In the modification shown in FIG. 16C, the leg portion 33 has a semi-cylindrical shape elongated in the width direction of the main member 32 . Two leg portions 33 are attached to both ends in the length direction of the bottom surface of the main member 32, respectively, with the cylindrical surface facing downward. In the modification shown in FIG. 16C as well, the reference device 30 is supported on the upper surface of the workpiece 12 at two points in the length direction. In the modification shown in FIG. 16B, the leg 33 is in surface contact with the work 12, but in the modification shown in FIG. 16C, the leg 33 is in line contact with the work 12. Therefore, in the modification shown in FIG. 16C, the reference device 30 can be more stably supported on the upper surface of the workpiece 12 than in the modification shown in FIG. 16B. The shape of the leg portion 33 does not necessarily have to be a semi-cylindrical shape, and may be any shape that makes line contact with a plane along a straight line parallel to the width direction of the main member 32 .

In the modification shown in FIG. 16D, four hemispherical legs 33 are attached to the four corners of the bottom surface of the main member 32 . In the modification shown in FIG. 16D as well, the reference device 30 is supported on the upper surface of the workpiece 12 at two points in the length direction.

As described above, in the modification shown in FIGS. 16A to 16D as well, the reference device 30 has a support structure that supports it at two locations in the longitudinal direction. Therefore, as in the case of the embodiment shown in FIG. 5, the shape of the bending of the reference surface 31 does not depend on the uneven shape of the upper surface of the work 12 when it is placed on the upper surface of the work 12 . Therefore, by _performing zero point calibration of the detector 40 using the reference device 30 by the method described with reference to FIG. The zero point offset amount g ₀ can be determined so that the true zero point B ₀₁ of 42b and the zero point C ₀ of the third displacement gauge 42c are positioned on a straight line.

Next, referring to FIGS. 17A and 17B, reference device 30 according to another modification of the embodiment shown in FIG. 5 will be described.

17A is a side view of the reference device 30 in zero gravity, and FIG. 17B is a side view of the reference device 30 placed on the upper surface of the workpiece 12. FIG. In the embodiment shown in FIG. 5, when the reference device 30 is placed on the upper surface of the workpiece 12, the reference surface 31 is flexed to be convex downward. On the other hand, in this modified example, the reference surface 31 (FIG. 17A) is curved so as to be convex upward in the weightless state. When the reference device 30 is placed on the upper surface of the work 12, the reference device 30 is bent due to its own weight. The shape of the reference plane 31 (FIG. 17B) after deflection is a geometrically correct plane.

In the modification shown in FIGS. 17A and 17B, the reference plane 31 is flat with the reference device 30 placed on the upper surface of the workpiece 12, so the zero point offset _g0 of the detector 40 is zero. Therefore, the offset amount g can be calculated using equation (1) instead of equation (4).

In the above embodiment, the detector 40 has a total of three displacement gauges, ie, the first displacement gauge 42a, the second displacement gauge 42b, and the third displacement gauge 42c. may be

It goes without saying that each of the above-described embodiments and modifications are examples, and partial substitutions or combinations of configurations shown in different embodiments are possible. Similar actions and effects due to similar configurations of multiple embodiments will not be sequentially referred to for each embodiment. Furthermore, the invention is not limited to the embodiments described above. For example, it will be obvious to those skilled in the art that various changes, improvements, combinations, etc. are possible.

10 movable table 11 table guide mechanism 12 workpiece 15 grindstone head 16 grindstone 18 guide rail 20 control device 21 input/output device 22 measurement display pane 23 basic setting pane 24 calibration pane 25 calibration start button 26 measurement start button 27 temperature measurement button 28 Message prompting zero point calibration 29 Past measurement result pane 30 Reference device 31 Reference surface 32 Main member 33 Leg 40 Detector 41 Support base 42a First displacement gauge 42b Second displacement gauge 42c Third displacement gauge 45 Temperature sensor

Claims (9)

a detector that includes at least three displacement gauges arranged in a line and is arranged facing the measurement object to detect the displacement of the distance from the at least three displacement gauges to the measurement object;
a datum supported on a support member to provide a reference surface for calibration of the detector;
and a controller for calibrating the detector ,
The reference device has a support structure supported on the support member at two points in the direction in which the at least three displacement gauges are arranged,
The shape measuring device, wherein the control device calibrates the detector with the reference plane facing the at least three displacement gauges. The reference device has a shape elongated in one direction,
The support structure includes three legs protruding from a bottom surface opposite the reference plane, two of the three legs being at the same position with respect to the length of the datum. The shape measuring device according to claim 1, wherein the shape measuring device is arranged in a detector that includes at least three displacement gauges arranged in a row and is arranged facing the object to be measured to detect the displacement of the distance from each of the at least three displacement gauges to the object to be measured; ,
a datum supported on a support member to provide a reference surface for calibrating the detector;
and a controller for calibrating the detector ,
In a state in which the reference device is supported on the support member, it is bent by its own weight, and the shape of the reference surface in the bent state is not affected by the unevenness of the upper surface of the support member. ,
The shape measuring device, wherein the control device calibrates the detector while the at least three displacement gauges face the reference plane. The control device stores a shape of deflection that occurs in the reference surface when the reference device is placed on the support member, and calibrate the detector based on the stored shape of deflection. Item 4. The shape measuring device according to any one of Items 1 to 3. moreover,
an input/output device for inputting commands to the control device and for outputting measurement results by the control device;
a temperature sensor that measures the temperature of a location where the temperature of the detector is reflected;
The shape measuring device according to any one of claims 1 to 4, wherein the control device outputs to the input/output device a value measured by the temperature sensor at the time of the most recent calibration and a value measured by the temperature sensor at the present time. . When the difference between the value measured by the temperature sensor at the time of the most recent calibration and the value measured by the temperature sensor at the current time exceeds a threshold, the control device provides alert information prompting calibration of the detector from the input/output device. 6. The shape measuring device according to claim 5, which outputs the . The control device is
measuring and storing the straightness of the surface of the object to be measured while moving one of the object to be measured and the detector with respect to the other in the direction in which the at least three displacement gauges are arranged;
7. The shape measuring apparatus according to claim 5, wherein a plurality of measurement results of straightness of the surface of the object to be measured are output to said input/output device in a form that enables comparison. When calibrating the detector, the controller moves the reference device supported on the support member relative to the detector by moving the support member relative to the detector. The shape measuring device according to any one of claims 1 to 7, wherein the shape measuring device is moved. Calibration of a detector that detects the displacement of the distance from each of the at least three displacement gauges to the measurement object by arranging at least three displacement gauges arranged in a line so as to face the measurement object a method,
supporting the reference device on a supporting member at two locations in the direction in which the at least three displacement gauges are arranged, in a posture in which the reference surface of the reference device faces the at least three displacement gauges;
A calibration method for calibrating the detector with the at least three displacement gauges facing the reference plane.

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